Pentameric PdAu and PdPt nanoparticles on the MgO(100) surface and their CO and O2 adsorption properties

The surface mode of the Birmingham Cluster Genetic Algorithm (S-BCGA), which performs an unbiased global optimisation search for clusters adsorbed on a surface, has been employed for the global optimisation of noble metal pentamers on an MgO(100) substrate. The effect of element identity and alloying in surface-bound neutral subnanometre particles is calculated by energetic analysis of all compositions of supported 5-atom PdAu and PdPt clusters. Our results show that the binding strengths of the component elements to the surface are in the order Pt > Pd > Au. In addition, alloying Pd with Au and Pt is favorable for this size since excess energy calculations show a preference for bimetallic clusters for both cases. Furthermore, the electronic behaviour, which is intermediate between molecular systems and bulk metals allows tuning of the characteristics of particles in the subnanometre size range. The adsorption of CO and O-2 probe molecules are also modelled and it is found that CO and O-2 adsorption leads to a weakening of the cluster-surface interaction.